Unable to load Portfolio plan pages Edited

I am working with a customer in a Jira 7.5.0 Setup with Portfolio 2.6.1 plugin. When we try to create a plan or display plan, system comes back with a message "Bummer, something has gone terribly wrong", suggesting to refresh the page (didn't work) or contact Administrator or Atlassian Support providing some kind of frontend stacktrace.

The stacktrace shows the following:

As you can see in the picture, there seems to be an issue with jpo-wr-page-plan-scripts.js script. I did some google search and i was unable to find this specific issue anywhere, however i have found relatable issues like.